Molding press



Feb. 23, 193 7.

, I A. M. HOWALD HOLDING PRESS F:l .1ed June 1;, 1935 3 Sheets-Sheet 1Arthur M Hawk INVENTOR ATTORNEY Feb. 23, 1937. A. M. now/m: 2,071,795

' MOLDING PRESS Filed June 11. 1935 3 Sheets-Sheet 2 ATTORNEY Feb. 23,1937. A. M. HowALD 4 5 MOLDING PRESS Filed June 11, 1935 I sSheets-Sheet s Arthur M hbwob lNVENT R ATTORNEY Momma rss Arthur M.Howaid, Toledo, Ohio, oasis-nor, by memo assignments, to PlaskonCompany, In corporated, a corporation oi Application June n, 1935,Serial No. 26,085

8 c (ciao-'52 This invention relates to molding presses, and itsprincipal objectisto provide. an electrically= operated hydraulic presshaving means for bringing the molding material quickly into engagementwith the plunger of the mold and tor thereafter moving the mold sectionstoward each other with uniform speed during flow of the molding materialand, after the molding material has flowed to the shape of the mold,maintaining it under den nite pressure for a definite time.

Other objects and advantages will be apparent from the followingdescription, in which reference is had to the accompanying drawingsillus tratlng a preferred embodiment of my invention and wherein similarreference numerals desig nate similar parts throughout the severalviews.

In the drawings: Figure I is a side elevational view of a molding pressembodying my invention.

Figure 11 is an end elevational view of the molding press shown inFigure I.

Figure III is a partial plan view taken substan tiallyalong the lineIH-III of Figure I, a motor supporting frame and the partscarriedthereby being removed-and parts of the piping being broken away.

Figure IV is an enlarged fragmentary eleva= tional view, partlyinsection, taken along the line IV-IV of Figure, 111. v

Figure V is a wiring diagram showing circuits employed in controllingthe operation of the molding press.

Figure VI is an enlarged sectional view showing the interior of a pumpemployed in the deviceoi my invention.

Referring to the drawings in detail, the mech anism is mounted upon abox-like base i having a horizontal shelf-like extension 2 supporting .aframe 3 upon which a reversible motor t is rigidly mounted. The motor thas a motor slit 5 extending from both ends, and one end of the shaft 5is connected to a speed reducer ii, the otherend being connected, bymeans of a self aligning collar '3, to a double acting, large capac ity,low pressure oil pump 9. Onthe shelf=lihe extension iis bolted anotherspeed reducer 9, which is driven from the speed reducer t by means ofsprockets it and ill and a roller chain it, and is connected by means ofa collar it to a shaft it (see Figure m).

Also bolted to the shelf-like extension 2 is a bracket 55 encasing aball hearing it in which the shaft it is journaled, the shaft it beingheld by adjustable thrust collars I'I against endwise movement and beingformed beyond the hearing it into a screw it (see Figures I and III). Ahigh pressure ram I9 is rigidly mounted upon the shelf-like extension 2by means of brackets 20. The ram is consists principally of a ramcylinder 23, having its interior bored and receiving a piston 2 l. Thepiston 2! has a short interiorly threaded portion at 22, the remainderof its lnte-. rior being hollow and of sufflcient diameter to freelyreceive the screw it. Projections 24 on the ram cylinder and tlon thebearing bracket it are rigidly connected'by shouldered rods 28, andprojections 21! on the piston are provided with openings to receive therods 26 and slide thereon, the purpose of the rods 26 being to align andguide the piston and to prevent twisting movement from being imparted bythe screw to the piston. A packing gland Ed is mounted in the end of theram cylinder 23 to prevent leakage of oil.

An intake pipe 29 leads from an oil reservoir (not shown) to the largecapacity, low pressure pump 8. The pump 8 is of the gear type. When thegears are driven in the direction indicated by the slotted arrows inFigure VI the oil is drawn in through the intake pipe 29 and dischargedthrough the piping til. From one of the outlets of the pump 8, piping1th, in which is interposed a relief valve iii connected to a returnpipe 32, for a pose which will be hereinafter explained,

leads to a check valve 3-3, the check valve being connected to a sideoutlet 1" 34 by means of an elbow ea one end of the side outlet T he isscrewed into the opening at the discharge end otthe ram cylinder 23.Another end of the T.

til is connected by means of a pipe lit and a T 3? into an hydraulicpress cylinder he (see Figure The side outlet of the i he is connec to acontactpressure gauge 39 by means of a pipe Qt.

A pipe bl, leading from the i Si, is connected by means of an elbow $2to a valve it operated by a solenoid lit, and there is also an outletpipe ti l leadingv from the solenoid-operated valve db to the oilreservoir. The purpose of the solenoidoperated valve and the outlet pipewill be apparent when the description of the electrical control syst isreached. The cylinder 33 is rigidly mounted upon the box-like base i bymeans of cap screws t5, and a plate 58 is welded in an annular under-cutportion M of the cylinder st to prevent'leakage of oil. The inner wallof the cylinder 38 is bored to receive an accurately machined piston 68.In the upper end of the cylinder St is machined an annular groove 59, m11 which pacmng and an adjust-ably mounted paclsi ring ht are secured toprevent oil leakage and consequent pressure decrease. A movable table 5|is secured to the top of the piston 48 by means of cap screws and isprovided with three guide sleeves 52, 53 and 54, which are adaptedrespectively to receive guide shafts 55, 56 and 51. The guide sleevesare provided with adjustable positioning rings 58 to insure properlocation of the table 5!. The guide shafts are threaded at their lowerends into a rigid member 59 lying within the box-like base I andengaging the inside of the top of the base directly under the cylinder38, for the purpose of counteracting strains caused by downward pressureof the cylinder upon the base. The upper ends of the guide shafts 55, 56and 51 are threaded and secured by nuts 68 and 6| to a stationary head62.

Projections 63 onthe movable table 5| carry ejector pistons 64 andslidably receive rods 65,

the rods being bolted beneath the shelf-like extension 2 and rigidlysupporting ejector or pullback cylinders 66 and holding them from upwardmovement due to reactive force when pressure is applied to the ejectorpistons. The ejector cylinders are provided with packing and adjustablepacking rings 61 to prevent leakage of oil and loss of pressure. Piping68 from the other outlet of the low pressure pump 8 leads to the top ofthe ejector cylinders, the piping 68 including a relief valve (notshown) identical in construction to the relief valve 3|, but adjusted toopen at lower pressure.

In molding certain materials, application of heat during the moldingoperation is necessary, and, therefore, I have provided pipes 69, withflexible tubes 18 and 1|, which are connected into the molding block 12and plunger 13 to supply any suitable heating fluid, preferably hot oil.

Referring to the wiring diagram (Figure V), current is supplied fromthetrunk line indicated by the numerals 14 and 15 to a switch 16, which,when closed, permits current to flow through a wire 18 and through anormally closed limit switch 19, and thence through a wire 88 to anormally open push-button starting switch 11. When the push-buttonstarting switch 11 is closed, current can flow through a normally closedpush-button stop switch 8| and through a wire 82 and the contacts of anormally closed relay 83 and energize the coil of a relay 84, thuscausing the current to pass around the starting switch 11 and continueto flow through the wire 85 after the starting switch 11 is opened. Thecurrent flows through the normally closed contacts of the contactpressure gauge 39 and thence through the lead 86 to a normally closedlimit switch 81.

' The limit switch 81 is only opened in case the piston 2| of the ram l9moves forward to substantially its limit of movement, the limit switch81 being interposed in the line to the motor 4 to stop the motorwhenever the piston 2| reaches its limit of movement. This condition.rarely occurs. From the limit switch 81 current passes to the forwardwinding 88 of the reversible motor 4, causing the motor to travel in aforward direction,'thus operating the large capacity, low pressure pump8 and the high pressure ram 19. forcing oil into the hydraulic presscylinder 38 and causing the piston 48 to rise rapidly until itencounters resistance because of engagement of the molding material withthe plunger section of the mold, whereupon the relief valve 31 opens andthe oil which is pumped by the large capacity, low pressure pump 8 isreturned to the reservoir through the return pipe 32.

The ram l9 continues to force oil into the hydraulic press cylinder 38and increase the pressure in the hydraulic press cylinder and in thecontact pressure gauge 39. So long as the contacts .of the contactpressure gauge 39 remain closed, current passing through the contacts,and then through a wire 86 to a wire 89, energizes the coil of anormally closed relay 98, thus preventing the flow of current throughtherelay. When pressure in the contact pressure gauge 39 has increasedsufliciently to open the contacts of the contact pressure gauge, theforward winding of the motor is no longer energized and the motor stops.At the same time, the relay 98 is de-energized and current flows througha wire 9|, the contacts of the relay 98, and a wire 92, energizing thecoil of a normally open relay 93. Thereafter current from the wire 85goes through a wire 94, through the -closed contacts of the relay 93,and thence through wires and 95, and energizes the heating coil 91 of athermostatically-controlled delayed-action relay 98. Although the motoris stopped, the pressure in the hydraulic press-cylinder 38 and thecontact pressure gauge 39 is maintained so long as thethermostatically-controlled delayed-action relay does not close and solong as the piston 48 of the hydraulic press does not yield and there isno leakage in the oil pressure system. The contact pressure gauge may beso adjusted that the contacts are opened at any predetermined pressureand in practice the gauge is so adjusted that the contacts are notopened until the molding material has flowed to the shape of the moldand the mold is closed, after which the piston 48 of the hydraulic pressceases to yield to the pressure of the oil. Current passing through theheating coil 91 of the thermostatically-controlled delayed-action relay98 is sufllcient to heat the thermostat but not suflicient to energizethe relay 83. The thermostat may be adjusted to close the delayed-,action relay after the predetermined interval during which it isdesired that pressure be maintained upon the material in the mold.

When, after such predetermined interval, the thermostatically-controlleddelayed-action relay 91 closes, the relay 83 is energized, breaking thecircuit through its contacts and de-energizing the relay 84, therebyproviding a path for current from a wire I88 to a wire IN and the limitswitch 99 (which was closed when the piston 2| started to move into thecylinder 23 of the ram I9). The current passing through the wire I81 andthe closed limit switch 99 energizes the reverse wind-' ing I82 of thereversible motor 4, causing the motor and speed reducing mechanism toturn backwardly and the piston 2| to back out of the cylinder 23 of thehydraulic ram 19 until the contacts of the limit switch 99 are opened.At the same time current is supplied to the reverse winding I82 of thereversible motor 4, current is also supplied to the solenoid coil of thesolenoid 43' operating the valve 43, which opens and permits oil to flowfrom the cylinder 38 of the hydraulic press back to the reservoir. Thenormally closed limit switch 19 is opened by the upstroke of thesolenoid-operated valve 43 and serves as a safety means to preventcurrent from passing to both the forward coil 88 and the reverse coill82 of the reversing motor 4 at the same time, if the starting button 11should be closed for the purpose of starting the device before the cycleis complete. When the piston 2| opens the contacts of the limit switch99, the reverse winding of the motor 4 and the solenoid coil of thesolenoid-operated valve 43 both are de-enu a: the atically ergizedandthe electrical system an: condition in which it is shown in Figure V. da

If prior to the closing of-thethermostatically controlled delayed-actionrelay 98 the'pressure on the contact pressure gauge 88 should fall causeof yielding of the hydraulic press piston W or because of oil leakage.the contacts of the contact pressure gauge would close tne current againgauge 39 caused byvdecreasing and increasing pressure will not affectthe time of operation of the thermostatically-controlled delayed-actionrelay 98. The pressure in the hydraulic press cylinder 38 thus ismaintained at approximately the point at which the contacts of thecontact pressure gauge 39 are set to open eventhough the hydraulic presspiston 48 may yield slightly or slight leakage of oil may take place.

e relays of the electrical control system are housed in a cabinet I03which is mounted beneath the shelf-like extension 2 of the base.

In the operation of the device, the properquantity of molding compoundis placed in the heated lower mold section I2 andthe starting button His pressed. The reversible motor d travels in a forward direction,driving thepump 8, which forces oil at a rapldrate into the cylinder 38.The motor at the same time drives the speedreducersii and 9, which, inturn, operate the screw it, forcing the piston 2i slowly into thecylinder 23 of the high pressure ram l9, so that the high pressure ramalso forces oil into the hydraulic press cylinder 38, but at a muchslower rate. When the lower section 12 of the mold has risen intoposition in whichthe molding material is brought into engagement withthe mold plunger 13 of the mold, the pressure in the hydraulicpresscylinder '38 quickly rises to a point at which the relief valve 3|opens, and the oil passing through the pump is returned throughlthe pipe32 into the reservoir. The check valve 3 prevents escape of oil from thehigh pressure ram cylinder 23 and the hydraulic press cylinder 38through the relief valve 3|. Hence the piston continues to rise atgreatly reduced speed as oil is forced from the cylinder 23 of the highpressure ram it into the hydraulic press cylinder 38, and the moldingmaterial is forced into the shape of the mold.

- The pressure inthe hydraulic press cylinder is transmitted to thecontact pressure gauge 39, and

when the pressure has risen to the limit at which the contacts of thecontact pressure gauge are 75 tion relay closes, whereupon thesolenoid-actu lic press cylinder 38 to flow back, to the oil reservoir.The motor turns in reverse direction (as in-.

dicated by thebroken arrows in Figure VI) ,--to'. withdraw the pistonZtfrom the cylinder 23 of the high pressure ram IQto pump oil'throughthe pipe 88 to the ejector cylinders 68 and exert a downward push on thetable 5lsuflicient to tor cylinders being returned to the reservoirthrough a relief -valve (notv shown). After the mold is broken apart thetable will settle by its own weight as oil flows from the hydraulicpress cylinder 38, but'the pressure'in the elector cylinders 66 servesto overcome any tendency that'atedvalvefdopenstoallowoilfromthehydrauopen the'mold and start thetable downwardly,

oil pumped in excess of the capacity of the ejec- 1o the table may haveto stick above itslowermost position. p

After the starting series of operationgtakes place automaticaly. Byadjusting the position of the contacts of the contact pressure gauge 38,any predetermined final pressure may be employed in the molding'operation, and by adjusting the thermostaticallycontrolleddelayed-action relay 98 the pressure may be maintained for any desiredinterval The-embodiment of my invention herein shown and described is tobe regarded as illustrative only, and it is to be understood that theinvention is susceptible to variation, modification and Joined e 7Having described my invention, I claim:

1. In a device of the class. described, in combination, a hydraulicpress cylinder, a piston movable therein, a high capacity pump forforcing liquid into said hydraulic press cylinder, 9. high pressure ramfor also forcing liquidinto said hydraulic press cylinder, means for:separately and simultaneously operating said pump. and ram, meansoperative upon the attainment of'a comparatively low pressure forautomatically causing liquid from said pump to cease to flow into saidhydraulic press cylinder, means operative upon attainment of a higherpressure for automatically stopping the action of said high pressureram, and means operative after a predetermined interval forautomatically returning said high pressure ram to its initial condition.

2. In a device of the class described, in combination, a hydraulic presscylinder, a piston movable therein, ahigh capacity pump for forcingliquid into said hydraulic press cylinder, 2. high pressure ram for alsoforcing liquid into "said hydraulic press cylinder, means operative uponthe attainment of a comparatively low pressure for automatically causingliquid from said pump to cease to flow into said hydraulic'presscylinder, means operative upon attainment of a higher pressure forautomatically stopping the action of said high pressure ra'm meansoperative after a.predetermined interval for automatically returningsaid high pressure ram to its initial condition, and means operativealso after said predetermined interval for automatically dischargingliquid from said hydraulic press cylinder.

3. In a device of the class described, in combination, a hydraulic presscylinder, a piston movable therein, a high capacity pump for forcingliquid into said hydraulic press cylinder, 9. high pressure ram for alsoforcing liquid into said hydraulic press cylinder, means for separatelyand simultaneously operating said pump and ram, a relief valve operativeupon the attainment of switch 11 has closed, the

s change within the spirit and scope of the subl a comparatively lowpressure for'automatically 7g causing liquid from said pump to cease' toflow into said hydraulic press cylinder, means operative upon attainmentof a higher pressure for automatically stopping the action of said highpressure ram, and means operative after a predetermined interval forautomatically returning higher pressure for automatically stopping theaction of said high pressure ram, means operative after a predeterminedinterval for automatically returning said high pressure ram to itsinitial condition, and means operative also after said predeterminedinterval for automatically dischargingliquid from said hydraulic presscylinder.

5. In a device of the class described, in com-, bination, a hydraulicpress cylinder, a piston movable therein, a high capacity pump forforcing 1 liquid into said hydraulic press cylinder, a high pressure ramfor also forcing liquid into said hydraulic press cylinder, means forseparately and simultaneously operating said pump and ram, meansoperative upon the attainment of a comparatively low pressure forautomatically causing liquid from said pump to cease to flow into saidhydraulic press cylinder, means operative upon attainment of a higherpressure for automatically stopping the action of said high pressureram, and means operative after a predetermined interval for forcing thepiston of said hydraulic press backwardly toward its initial position.

6. In a device of the class described, in combination, a hydraulic presscylinder, a piston movable therein, a. high capacity pump for forcingliquid into said hydraulic press cylinder, a high pressure ram for alsoforcing liquid into said hydraulic press cylinder, a reversiblemotor foroperating said pump and said ram, a relief valve for automaticallydischarging liquid from said pump upon the attainment of a comparativelylow pressure in said hydraulic press cylinder, means operative upon theattainment of a higher pressure in said hydraulic press cylinder for,stopping said motor, and means automatically operative after apredetermined interval for causing said motor to rotate in-reversedirection and back said ram.

7. In a device of theclass described, in combination, a hydraulic presscylinder, a-pi'ston movable therein, a high capacity pump for forcingliquid-into said hydraulic press cylinder, a high pressure ram for alsoforcing liquid into said hydraulic press cylinder, a reversible motorfor operating said pump andsaid ram, a relief valve for automaticallydischarging. liquid from said pump upon the attainment of acomparatively low. pressure in said hydraulic press cylinder, meansoperative upon the attainment of a higher pressure in said hydraulicpress cylinder for stop- I ping said motor, means automaticallyoperative after a predetermined interval for causing said motor torotate in reverse directionand back said ram, and means automaticallyoperable also after said'predetermined interval for discharging theliquid from said hydraulic press cylinder.

bination, a hydraulic press cylinder, a piston movable therein, a highcapacity pump for forcing liquidinto said'hydraulic press cylinder, ahigh pressure ram for also forcing liquid into said '8. In a device ofthe class described, in comv pressure-in said hydraulic press cylinderfor stopping said motor, means automatically operativeiio after apredetermined intervalfor causing said motor to rotatein reversedirection, means automatically operable also aftersaid predeterminedinterval fordischarging the liquid from said hydraulic press cylinder,and means operative upon turning of said motor in reverse direction toforce said piston toward its initial position in said hydraulic presscylinder.

ARTHUR M. HOWALD.

